66 research outputs found
Proposal of a topological M(atrix) theory
Keeping in mind the several models of M(atrix) theory we attempt to
understand the possible structure of the topological M(atrix) theory
``underlying'' these approaches. In particular we are motivated by the issue
about the nature of the structure of the vacuum of the topological M(atrix)
theory and how this could be related to the vacuum of the electroweak theory.
In doing so we are led to a simple topological matrix model. Moreover it is
intuitively expected from the current understanding that the noncommutative
nature of ``spacetime'' and background independence should lead to a
topological Model. The main purpose of this note is to propose a simple
topological Matrix Model which bears relation to F and M theories. Suggestions
on the origin of the chemical potential term appearing in the matrix models are
given.Comment: 14 pages revte
Strings Inside Walls in N=1 Super Yang-Mills
We conjecture the existence of strings bounded inside walls in SU
Super Yang-Mills theory. These strings carry quantum number, where
is the greatest common divisor between , the charge of the wall, and
. We provide field-theoretical arguments and string-theoretical evidences,
both from MQCD and from gauge-gravity correspondence. We interpret this result
from the point of view of the low-energy effective action living on the
-wall.Comment: 25 pp. Major changes. In particular, following the recent work
arXiv:0807.1908 we have been able to give a field theoretical proof of the
statement. We have also corrected an important erroneous interpretation in
the previous version regarding the 2+1 effective action; Typo
A Geometric Unification of Dualities
We study the dynamics of a large class of N=1 quiver theories, geometrically
realized by type IIB D-brane probes wrapping cycles of local Calabi-Yau
threefolds. These include N=2 (affine) A-D-E quiver theories deformed by
superpotential terms, as well as chiral N=1 quiver theories obtained in the
presence of vanishing 4-cycles inside a Calabi-Yau. We consider the various
possible geometric transitions of the 3-fold and show that they correspond to
Seiberg-like dualities (represented by Weyl reflections in the A-D-E case or
`mutations' of bundles in the case of vanishing 4-cycles) or large N dualities
involving gaugino condensates (generalized conifold transitions). Also duality
cascades are naturally realized in these classes of theories, and are related
to the affine Weyl group symmetry in the A-D-E case.Comment: 94 pages, 18 figures. Added referenc
Orientifolds, Unoriented Instantons and Localization
We consider world-sheet instanton effects in N=1 string orientifolds of
noncompact toric Calabi-Yau threefolds. We show that unoriented closed string
topological amplitudes can be exactly computed using localization techniques
for holomorphic maps with involution. Our results are in precise agreement with
mirror symmetry and large N duality predictions.Comment: 25 pages, 10 figures, published version; v4: typos correcte
Orientifolds of K3 and Calabi-Yau Manifolds with Intersecting D-branes
We investigate orientifolds of type II string theory on K3 and Calabi-Yau
3-folds with intersecting D-branes wrapping special Lagrangian cycles. We
determine quite generically the chiral massless spectrum in terms of
topological invariants and discuss both orbifold examples and algebraic
realizations in detail. Intriguingly, the developed techniques provide an
elegant way to figure out the chiral sector of orientifold models without
computing any explicit string partition function. As a new example we derive a
non-supersymmetric Standard-like Model from an orientifold of type IIA on the
quintic Calabi-Yau 3-fold with wrapped D6-branes. In the case of supersymmetric
intersecting brane models on Calabi-Yau manifolds we discuss the D-term and
F-term potentials, the effective gauge couplings and the Green-Schwarz
mechanism. The mirror symmetric formulation of this construction is provided
within type IIB theory. We finally include a short discussion about the lift of
these models from type IIB on K3 to F-theory and from type IIA on Calabi-Yau
3-folds to M-theory on G_2 manifolds.Comment: 82 pages, harvmac, 5 figures. v2: references added. v3: T^6
orientifold corrected, JHEP versio
Supersymmetric Three-Form Flux Perturbations on
We consider warped type IIB supergravity solutions with three-form flux and
supersymmetry, which arise as the supergravity duals of confining
gauge theories. We first work in a perturbation expansion around , as in the work of Polchinski and Strassler, and from the
conditions and the Bianchi identities recover their first-order solution
generalized to an arbitrary superpotential. We find the second
order dilaton and axion by the same means. We also find a simple family of
exact solutions, which can be obtained from solutions found by Becker and
Becker, and which includes the recent Klebanov--Strassler solution.Comment: 19 pages. reference added, minor clarifications. v3: reference to
non-Abelian BPS monopole solution corrected (Chamseddine-Volkov
Local models for intersecting brane worlds
We describe the construction of configurations of D6-branes wrapped on
compact 3-cycles intersecting at points in non-compact Calabi-Yau threefolds.
Such constructions provide local models of intersecting brane worlds, and
describe sectors of four-dimensional gauge theories with chiral fermions. We
present several classes of non-compact manifolds with compact 3-cycles
intersecting at points, and discuss the rules required for model building with
wrapped D6-branes. The rules to build 3-cycles are simple, and allow easy
computation of chiral spectra, RR tadpoles and the amount of preserved
supersymmetry. We present several explicit examples of these constructions,
some of which have Standard Model like gauge group and three quark-lepton
generations. In some cases, mirror symmetry relates the models to other
constructions used in phenomenological D-brane model building, like D-branes at
singularities. Some simple N=1 supersymmetric configurations may lead to
relatively tractable G_2 manifolds upon lift to M-theory, which would be
non-compact but nevertheless yield four-dimensional chiral gauge field
theories.Comment: 52 pages, latex, 24 enclosed eps figures; v2. typo correcte
The Footprint of F-theory at the LHC
Recent work has shown that compactifications of F-theory provide a
potentially attractive phenomenological scenario. The low energy
characteristics of F-theory GUTs consist of a deformation away from a minimal
gauge mediation scenario with a high messenger scale. The soft scalar masses of
the theory are all shifted by a stringy effect which survives to low energies.
This effect can range from 0 GeV up to ~ 500 GeV. In this paper we study
potential collider signatures of F-theory GUTs, focussing in particular on ways
to distinguish this class of models from other theories with an MSSM spectrum.
To accomplish this, we have adapted the general footprint method developed
recently for distinguishing broad classes of string vacua to the specific case
of F-theory GUTs. We show that with only 5 fb^(-1) of simulated LHC data, it is
possible to distinguish many mSUGRA models and low messenger scale gauge
mediation models from F-theory GUTs. Moreover, we find that at 5 fb^(-1), the
stringy deformation away from minimal gauge mediation produces observable
consequences which can also be detected to a level of order ~ +/- 80 GeV. In
this way, it is possible to distinguish between models with a large and small
stringy deformation. At 50 fb^(-1), this improves to ~ +/- 10 GeV.Comment: 85 pages, 37 figure
(Anti)symmetric matter and superpotentials from IIB orientifolds
We study the IIB engineering of N=1 gauge theories with unitary gauge group
and matter in the adjoint and (anti)symmetric representations. We show that
such theories can be obtained as Z2 orientifolds of Calabi-Yau A2 fibrations,
and discuss the explicit T-duality transformation to an orientifolded
Hanany-Witten construction. The low energy dynamics is described by a geometric
transition of the orientifolded background. Unlike previously studied cases, we
show that the orientifold 5-`plane' survives the transition, thus bringing a
nontrivial contribution to the effective superpotential. We extract this
contribution by using matrix model results and compare with geometric data. A
Higgs branch of our models recovers the engineering of SO/Sp theories with
adjoint matter through an O5-`plane' T-dual to an O6-plane. We show that the
superpotential agrees with that produced by engineering through an O5-`plane'
dual to an O4-plane, even though the orientifold of this second construction is
replaced by fluxes after the transition.Comment: 40 page
GUTs and Exceptional Branes in F-theory - I
Motivated by potential phenomenological applications, we develop the
necessary tools for building GUT models in F-theory. This approach is quite
flexible because the local geometrical properties of singularities in F-theory
compactifications encode the physical content of the theory. In particular, we
show how geometry determines the gauge group, matter content and Yukawa
couplings of a given model. It turns out that these features are beautifully
captured by a four-dimensional topologically twisted N=4 theory which has been
coupled to a surface defect theory on which chiral matter can propagate. From
the vantagepoint of the four-dimensional topological theory, these defects are
surface operators. Specific intersection points of these defects lead to Yukawa
couplings. We also find that the unfolding of the singularity in the F-theory
geometry precisely matches to properties of the topological theory with a
defect.Comment: v2: 121 pages, 5 figures, reference and clarification adde
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